1. Field of the Invention
The present invention relates to a method of producing an aromatic carbonate using a specified catalyst system. Aromatic carbonates, particularly diphenyl carbonate are useful as raw materials for polycarbonate or the like.
2. Description of the Related Art
A method of reacting an aromatic hydroxy compound with phosgene is generally used for producing an aromatic carbonate. However, this method is undesirable because of the high toxicity of phosgene.
Some methods have thus been proposed which do not use phosgene in which an aromatic carbonate is produced from an aromatic hydroxy compound, carbon monoxide and oxygen.
The catalyst used in such methods can be found in the following. U.S. Pat. No. 4,187,242 discloses a method which uses as a catalyst a palladium compound, a compound containing a metal selected from the group IIIA, IVA, VA, VIA, IB, IIB, VIB or VIIB in the periodic table, and a base. U.S. Pat. No. 4,201,721 discloses a method which uses a palladium compound, a manganese or cobalt complex, a base and a desiccating agent. Japanese Patent Laid-Open No. 1-16555 discloses a method which uses a palladium compound, iodine and zeolite. Japanese Patent Laid-Open No. 2-104564 discloses a method which uses a palladium compound, a divalent or trivalent manganese compound, tetraalkylammonium halide and a quinone. Japanese Patent Laid-Open No. 2-142754 discloses a method which uses a palladium compound, a divalent or trivalent cobalt compound, tetraalkylammonium halide and a quinone. Japanese Patent Laid-Open No. 5-25095 discloses a method which uses palladium or a palladium compound, a cobalt compound, a halide and a basic compound. Japanese Patent Laid-Open No. 5-39247 discloses a method which uses a palladium compound, a copper compound, a quinone and onium halide. Japanese Patent Laid-Open No. 5-58961 discloses a method which uses at least one of palladium and a palladium compound, a cobalt compound and alkali metal halide. U.S. Pat. No. 5,142,086 discloses a method which uses a catalyst system comprising palladium, quaternary ammonium salts, a metallic cocatalyst selected from cobalt, iron, cerium, manganese, molybdenum, samarium, vanadium, chromium and copper; and an organic cocatalyst selected from aromatic ketones, aliphatic ketones and aromatic polycyclic hydrocarbons. Japanese Patent Laid-Open No. 6-9505 discloses a method which uses a palladium compound, a cerium compound, and a quaternary ammonium salt. Japanese Patent Laid-Open No. 6-41020 discloses a method which uses palladium compounds, a metallic cocatalyst selected from manganese, cobalt and copper, and a nitrile compound. U.S. Pat. No. 5,231,210 discloses a method which uses a palladium compound, a cobalt pentacoordinate complex, and a quaternary onium salt. U.S. Pat. No. 5,284,964 discloses a method which uses an inorganic cocatalyst selected from palladium compounds; an inorganic cocatalyst selected from cobalt, manganese and copper; quaternary onium salts and terpyridine.
In the examples described in the above publications, the yield of aromatic carbonate per palladium (turnover number of palladium) is less than 700, and thus the catalyst activity is not always satisfactory.